| I think I get pushed the most harmonically when I work on melodic aspects of music.
From a simple two or three note melody can come so many harmonic ideas that it's just mind blowing. An exercise I use when I'm trying to come up with new harmonic sequences to work with is taking two notes a whole step apart for instance, and then figuring out all the possibly root not combinations with those two notes, just going back and forth between then in a quarter note pulse. Then once I have maybe 8 or 9 possibilities for root notes with each melody note I'll start to fill in different sounding harmonies in the middle. maybe starting with all major sounds, then trying dominant, then lydian, then minor... etc etc etc until I suddenly have this huge pallet of sounds to choose from having only started with two notes a whole step away from each other.
Then expand that with two notes a half step apart, a minor third apart, two notes a whole step apart but then move the root motion of the melody notes up the finger board in minor thirds..... the possibilities are pretty much endless. Your only barrier is your own imagination.
The other aspect of not being able to replicate ideas that you have in your head on the bass..... that is just time spent with the instrument. As long as you're inspired to do it, spend more and more time with the instrument, sing everything you play. Work on singing things away from the instrument so that when you pick up the bass you'll be able to place those ideas right away. It's working on the fundamentals of music that will really give you the building blocks of basic language to use as a foundation for any idea you have.
It's all like speech. You learned to speak as a baby from your parents constantly saying the same things to you over and over again. You started off with words like "hello" "mummy" "daddy" etc etc those words are like simple two notes phrases in music. a whole step, a half step, a minor third. Then you started to connect ideas and put things into sentences as you got older. This is just learning more phrases in music and making musical statements with them. Once you strip away the myth that seems to hang over improvised music, and realize that it's just yet another language to learn, it will become so much clearer. It'll also be apparent that it's not the easiest language to speak in the world, but that will make it clear as to what you have to do to reach a certain level of fluency so you can be understood by those you speak to.
And yeah, come by the show in the UK in November.... I think the only UK date for this tour will be the 17th of November in London for the London Jazz Festival.
Easy,
Janek | 
